I have the same circumstance...the single should be fine with a half sheet or so of a 3/4” plywood, bolt the stand in the corner...the 2 bike, maybe a whole sheet...maybe double up on at the bolt area.
One of my singles has angle iron feet...very stable...I do kick the front foot occasionally...the other single actually came with the plate...this is where I got the idea to bolt the stand in the corner of the half sheet...the double stand, I like the idea of the full sheet of plywood...stability and short $!
The metal plate on the single stand moves sometimes when I step on it as I’m working on my bikes...
pics coming...